canonical/node_modules/eslint-plugin-lodash/lib/rules/prefer-compact.js

Canonical code style linter and formatter for JavaScript, SCSS, CSS and JSON.

/**
 * @fileoverview Rule to check if a call to filter should be a call to compact
 */
'use strict';

//------------------------------------------------------------------------------
// Rule Definition
//------------------------------------------------------------------------------

module.exports = function (context) {
    var lodashUtil = require('../util/lodashUtil');
    var astUtil = require('../util/astUtil');
    var settings = require('../util/settingsUtil').getSettings(context);
    function isDoubleNegationOfParam(exp, paramName) {
        return astUtil.isNegationExpression(exp) && astUtil.isNegationExpression(exp.argument) && astUtil.isIdentifierOfParam(exp.argument.argument, paramName);
    }

    function isCallToBooleanCastOfParam(exp, paramName) {
        return exp && exp.type === 'CallExpression' && exp.callee.name === 'Boolean' && astUtil.isIdentifierOfParam(exp.arguments[0], paramName);
    }

    function isBooleanCastingFunction(func) {
        var returnValue = astUtil.getValueReturnedInFirstLine(func);
        var paramName = astUtil.getFirstParamName(func);
        return func && func.type === 'Identifier' && func.name === 'Boolean' ||
            (astUtil.isIdentifierOfParam(returnValue, paramName) ||
            isDoubleNegationOfParam(returnValue, paramName) || isCallToBooleanCastOfParam(returnValue, paramName));
    }

    return {
        CallExpression: lodashUtil.getLodashMethodVisitor(settings, function (node, iteratee) {
            if (lodashUtil.isCallToMethod(node, settings.version, 'filter') && isBooleanCastingFunction(iteratee)) {
                context.report(node, 'Prefer _.compact over filtering of Boolean casting');
            }
        })
    };
};